[PATCH/RFC future] nptl: reinstate SIGCANCEL/SIGSETXID safeguards

[Kevin Cernekee]

Commit 8ab3145f (remove sigaction, sigprocmask, and sigfillset from
libpthread) removed duplicated implementations of the three aforementioned
functions from libpthread.  However, as Rich Felker pointed out, the
libc and libpthread versions are not always 100% identical.  A closer
examination of the pre-8ab3145f disassemblies showed the following:

libc sigfillset() returns a full set: all 128 bits are set.  libpthread
sigfillset() sets only 126 bits: everything except SIGCANCEL/SIGSETXID.

libpthread sigprocmask() has extra code to prevent the caller from blocking
SIGCANCEL/SIGSETXID.  libc sigprocmask() does not.

No differences were observed in __sigaction(), since the NPTL version of
this function was always built into libc anyway.

This patch pulls in the SIGCANCEL/SIGSETXID definitions via pthreadP.h
when NPTL is enabled, restoring the special signal exclusions needed
by libpthread.

Signed-off-by: Kevin Cernekee <cernekee at gmail.com>
---
 libc/signal/sigfillset.c                |    4 ++++
 libc/sysdeps/linux/common/sigprocmask.c |    4 ++++
 2 files changed, 8 insertions(+), 0 deletions(-)

diff --git a/libc/signal/sigfillset.c b/libc/signal/sigfillset.c
index ef60f10..e041f08 100644
--- a/libc/signal/sigfillset.c
+++ b/libc/signal/sigfillset.c
@@ -23,6 +23,10 @@
 #include <errno.h>
 #endif
 
+#ifdef __UCLIBC_HAS_THREADS_NATIVE__
+#include <pthreadP.h>
+#endif
+
 /* Set all signals in SET.  */
 int
 sigfillset (sigset_t *set)
diff --git a/libc/sysdeps/linux/common/sigprocmask.c b/libc/sysdeps/linux/common/sigprocmask.c
index 6230033..a60fa49 100644
--- a/libc/sysdeps/linux/common/sigprocmask.c
+++ b/libc/sysdeps/linux/common/sigprocmask.c
@@ -9,6 +9,10 @@
 
 #include <sys/syscall.h>
 
+#ifdef __UCLIBC_HAS_THREADS_NATIVE__
+#include <pthreadP.h>
+#endif
+
 #if defined __USE_POSIX
 #include <signal.h>
 
-- 
1.7.5